Process for the manufacture of rubber dust



Patented June 7, 1938 v 7 UNITED STATES PATENT OFFICE PROCESS FOR THE MANUFACTURE OF RUB- BER DUST Martinus Joitnnes Stam, Ihe Hague, Netherlands No Drawing. Application August 30, 1935, Serial No. 38,653. In the Netherlands September 5, 19.3;

3 Claims. (Cl. 18-50) This invention relates to a new product which however, that rubber is to be taken in a general might be properly designated as rubber dust, sense, so not only rubber in the proper sense is latex dust or the like. meant, but also substances present in other It has been for a long time the object of. rubber latices than rubber latex, such as gutta percha,

5 experts to obtain rubber in the form of a powder balata and the like. 5 in order to avoid the need for heavy machinery The diameter of the globules or particles presin the rubber manufacturing industry. ent in latex dilTers between rather wide limits.

Many attempts in this direction have been The bulk of the rubber has a particle size bemade by which a crumb-like product is obtained tween 01 and 3 but also smaller and larger by various coagulating methods. particles are present. The particle size depends 10 By such methods, however, it is impossible to also on the age of the tree. In-trees of considerobtain a fine powder of pure rubber as desired by able age globules of somewhat larger size are experts. According to a publication by G. Martin frequent. in India Rubber Journal, December 3rd, 1932, in Whereas all previous products contain smaller order to obtain the same intimate mixture of rubor larger agglomerations of rubber particles, 5 ber and compounding ingredients as is obtained only the new product consists practically of rubwith compounded latex, the rubber powder would ber particles of the size in which they exist in probably have to consist of particles of less than latex. 1/1000 inch diameter. The new product is obtained by sub-dividing Other attempts to obtain a fine rubber powder latex into particles of substantially the size of have been made by spray drying latex to which the particles present in latex and drying 'the glue or haemoglobin have been added. These particles. In a preferred method the particles substances act as protective colloids and disare coated by a protective substance which prepersing agents and therefore the obtained rubber vents agglomeration of the same. 5 product may be easily re-dispersed in ammoniacal The way in which the latex is sub-divided into water into alatex-like liquid; but, by the methods particles of. the size described is immaterial; it known when the use of these protective colloids may be done by centrifugal action. In principle was disclosed, no powder of extreme fineness it is immaterial too in which way the particles are could be obtained. dried; it has been found advantageous to atomize I The first commercial product that may be the latex into a current of drying air. 30 really called rubber powder was obtained by The protective substance added to the latex applicant and this product and the manner by may be, for example, dextrine. which it is obtained is disclosed in his British It is true that the dry particles again adhere Patents No. 388,341 and No. 396,579. to each other probably due to static electrical nearly the same intimate mixture ofv rubber and gates which, however, are easily seen under a COInpOllIlding ingredients as is obtained with microscope to be separate particles in the same compounded latex. way as most other finely divided substances.

The particles of the rubber powder obtained In this manner, aggregates of a particle size of by these and other known methods vary in size about 01-75; may be formed, but these aggre- 40 but all consist of many elementary globules. The gates behave in the same way as the elementary finest powder obtained in this manner has a globules and differently from the known rubber particle size exceeding 75 1. powder.

Applicant has now found that a still better The following example will further illustrate product may be obtained from latex. one way of obtaining the rubber dust according 45 Such a product is a new commercial article of t t ti t th i ti is by no manufacture and it consists of rubber particles means restricted by this example. substantially of the size of the particles present in Example natural, preserved or artificial latex. The particles substantially have a size of less than 7511.. A th fi m of latex to which a Sub t ce s 50 In their preferred form the particles are coated been added 0813941018 of forming a Protective ye by a protective substance which prevents the round dried rub er globules w h p ev n h agglomeration of the particles. agglomeration of same, is atomized by a device In these documents rubber in the form derotating at 15,000 revolutions per minute having With this product it is indeed possible to obtain forces to a limited extent and form small aggre- 35 g scribed is called rubber dust. It is stated here, a diameter of 30 cm. or at 9000 revolutions per 55 r minute with a'device having a diameter of 50 cm. and spraying it in a drying current of air moving at a velocity of 250 'metres per second, which carries the droplets away as soon as they are formed, and prevents all agglomeration of droplets until they are perfectly dry.

In this example the small size of the particles formed which substantially is less than 75,, is

due to a combination of a high circumferential velocity of the atomizing device and a high velocity of the current of air.

What I claim is:

.1. Process for the manufacture of rubber dust from latex, comprising adding to latex a substance which prevents agglomeration of dried rubber particles, subdividing said latex entirely into small droplets and discharging these droplets into' a current'of drying gas of a suificient velocity to prevent uniting of the droplets before they are dried.

cient velocity to prevent uniting of the droplets before they are dried.

3. Process for the manufacture of rubber dust from latex comprising adding to the latexa substance which prevents agglomeration of dried rubber particles, subdividing said latex by centrifugal discharge from a rotating disc, having a circumferential velocity of about 450,0001r cm. per minute into a current of drying air of suificient velocity to prevent uniting of the droplets before they are dry.

MARTINUS JOANNES STAM. 

